Alarm Clock Oddity Again, Again, Again

This morning, I woke up two minutes before the alarm was set to go off.  I'm not sure what to make of this, but I think it's pretty interesting even if nobody else does.  What in a person's body/mind would cause them to wake up a minute or two before their alarm went off?  If one had an old school clock that you had to wind every day, maybe you could say that it was that hesitation and ticking sound that a clock like that makes 5 minutes before the hour (just like the clock on our fireplace mantle) but with a digital device, there's no explanation for any pre-alarm noises.  I'll go back and explain - we have an old antique wind-up clock on our fireplace mantle, and five minutes before the hour, the clock will make a distinct sound.  It's not very loud, but when you hear it day after day, you grow accustomed to the sound.  It's just a loud tick.  But as for me waking up a minute or two before my alarm goes off, I guess it's just my mind and body being in tune.  Who knows.